Field
The present invention relates to non-edible collagen casings for food products which do not have to be soaked in water or brine just before stuffing (ready-to-stuff casings), and the method for preparing them. More specifically, the invention refers to a preparation of a stabilized longlife non-edible collagen casing ready-to-stuff.
Related Technology
Collagen casings for food products have been used for a long time in sausages production as a substitution of natural casings. Collagen casings show a number of advantages in comparison with natural ones, like increase of stuffing productivity (bigger filling speed and lower frequency of stuffing interruptions due to casing breakages), more homogeneous and stable sausage caliber and length, and improved hygiene.
They are usually made of collagen obtained from bovine or porcine hides, which are washed, treated with alkali and acid, and ground until an extrudable acid gel is obtained. Then, collagen is extruded in a tubular shape film, cross-linked, dried to a low water content and reeled. Those reels are converted to fulfill the final customers' needs. Converting can be made by applying one or more of the following steps: shirring, tying, cutting, sewing, bundling or printing. Processes for production of these casings are described in U.S. Pat. Nos. 3,235,641, 3,579,358 and 3,930,035.
Collagen casings may be edible or non-edible. Non-edible casing is treated as a commodity, which normally shows higher diameter, higher degree of collagen cross-linking, and thicker wall (usually ca. 40-150 μm of a casing with 10-20% of humidity), than edible casing. As a consequence, non-edible casing texture is hard, tough and leathery, without the appropriate textural properties for mastication. So, non-edible casing is not eaten because of their unpleasant mouth feel, and it is normally peeled before the meat product encased therein is consumed. As non-edible casing is intended to be removed before eating the product, it has to be easy and fast peeled from the meat product, and the peeled casing shouldn't show adhered particles of meat. On the contrary, in an edible casing, it is a must to show good adherence to the meat product, like sausages stuffed with natural casing show.
Non-edible collagen casings can be used for the preparation of cooked or dry meat products. Common requirements for both types of application are good filling performance and good casing peelability from the meat product, as has been mentioned before. However, while casing for cooking has to stand the hydrothermal burden during cooking cycle, casing for a dry product has to be able to follow the volume reduction of the meat emulsion due to loss of water during maturation process. Usually two different types of non-edible collagen casing are produced for these different applications, which differ in the cross-linking degree.
The distinction between edible and non-edible collagen casings also affects the stuffing procedure. An edible casing doesn't need to be moistened and softened in water or brine before stuffing. So, those casings are stuffed directly. Non-edible casing has to be moistened and softened by soaking in water or in brine prior filling, in order to give them the necessary flexibility to make possible to put the casing upon the stuffing horn, and avoid casing breakages during stuffing and/or clipping. Low water content makes the casing too brittle and then casing bursts during filling and/or clipping step. Several pre-soaking procedures are applied by the meat-manufacturer to the non-edible collagen casing, prior to stuffing. Commonly brine is used, with different salt concentrations, soaking time and bath temperature, parameters that will depend on casing and converting type, produced sausage, stuffing machine, and other factors. In USA it is general the use of tap water and short soaking times. In the EP 03 445 126 patent a pre-soaking method for non-edible collagen casings is described for reinforcing the clip strength and cooking resistance thereof.
This pre-soaking step before stuffing is a time consuming period, and it needs the installation of tanks and equipment for preparing the brine. Also casings once soaked must be used in a short period of time of maximum one or two days. Additionally, soaking is a source of possible errors, like the lack of control in salt concentration, temperature and soaking exposure time, leading to a heterogeneous product and irregular stuffing performance. It is also a source of potential hygienic problems. Brine can also lead to speed up the corrosion of the stuffing area machinery. As a consequence, an additional cleaning is required in soaking and stuffing areas. Costs involved in the stuffing step of non-edible collagen casings are higher as more time, man power, maintenance, water and salt are required.
Another type of non-edible casings used for preparation of large caliber meat products, like plastic, fibrous and reinforced cellulose casings, have generally also to be moistened in water before stuffing, the same as non-edible collagen casings. Several prior art documents disclose different methods of preparation of a pre-moisturized, ready-to-stuff, plastic, fibrous and reinforced cellulose casings, in order to eliminate the pre-soaking in water prior to filling. Main problem to solve for these casings is the inhibition of microbial and mould or fungi growth in a casing with high water content. Two main different ways are used for preventing spoilage of such ready-to-stuff casings, (1) the use of huge amounts of plasticizers or humectants, like glycerin or propylene glycol, in order to decrease water activity (Aw) of the casing, and (2) the use of antimycotic agents, like alkyl esters of p-hydroxybenzoic acid. Processes for production of above mentioned casings are described in U.S. Pat. Nos. 3,617,312, 3,981,046, 4,409,251, 4,664,861, 4,867,204, and 6,279,737 patents. Plasticizers in huge amount and antimycotic agents could have adverse consequences, like blocking the natural indicators of food spoilage which are necessary for consumer safety, and disturb the normal development of the appropriate mould in the sausage surface, in the case of dry sausages.
In the specific field of non-edible collagen casings, we can find in prior art a successful development of a non-edible collagen ready-to-stuff casing.
SE-515441 describes a method of softening, stabilizing and preserving non-edible collagen casing for food products. Dry collagen casing is treated with a water-containing solution of sodium chloride in a concentration of 5-25% weight with a pH-value of 2,5-5,5 in a quantity large enough to ensure a water content of 30-50% weight and that a surplus of the sodium chloride solution of at least 5% weight remains on the surface of the collagen casing. Following the method described in that patent, it is possible to produce a non-edible collagen casing ready-to-stuff at industrial scale. In fact, round ready-to-stuff non-edible collagen casings were successfully commercialized by AB Tripasin casing Manufacturer Company.
But non-edible collagen casing ready-to-stuff prepared by the method disclosed in SE-515441 patent, showed a high degree of instability. Casings lost properties during stock at industrial scale. In fact, casing tensile strength, a parameter closely related to stuffing and clipping performance, decreased with stock time. Such casing tensile strength decrease was speeded up where temperature of the casing during stock and shipment to the customer was higher. It is likely that this is due to the fact that collagen hydrolysis took place, caused by the high level of water (30-50% weight) of the ready-to-stuff casing, leading to a weaker casing. This effect was enhanced during summer, where environmental temperature is high.
EP 1018301 also discloses a method of preparing a ready-to-stuff non edible collagen casing which does not need any additional soaking step before stuffing. Such casing comprises a moisture amount between 27% and 49% by weight based on total casing weight and a sodium chloride amount between 4 and 20% by weight based on dry casing weight. Dry collagen casing is soaked in an aqueous salt solution which concentration is between 5 and 25% during a period of time between 2 seconds and 60 seconds prior to the packing procedure.
In the case of EP 1018301, it is also possible to produce a non edible collagen casing ready-to-stuff at industrial scale. In fact, round and straight non-edible collagen casings were successfully commercialized by Naturin GmbH & Co casing Manufacturer Company. This casing, however, showed the same problems of instability, as with the product produced following the method described in patent SE-515441, because the amount of water in the casing is also in a high range (27-49% weight).
Due to the instability of non-edible collagen ready-to-stuff casings commercialized so far, there is a need in the market for a stabilized longlife non-edible collagen ready-to-stuff casing, with enough stability to be shipped and stored for a long period non refrigerated, at room temperature, without significant losses of stuffing performance. Such casing will also lead to a cost reduction, because it would not be necessary to prepare cool warehouses for stocking ready-to-stuff casings, neither use refrigerated transport for delivering casings to customers. A stabilized product like this will increase customers' confidence in a non-edible collagen casing ready-to-stuff.